The biology ofDendrocerus carpenteri(Hymenoptera: Ceraphronidae), a parasite ofAphidiusspecies, and field observations ofDendrocerusspecies as hyperparasites ofAcyrthosiphonspecies

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Abstract
Hyperparasitism by Dendrocerus species was found to occur at all sites from which the introduced pea aphid parasite Aphidius eadyi was recovered. D. carpenteri was more common than D. aphidum. The only other hyperparasite recovered was Phaenoglyphis sp., but this was rare. D. carpenteri was laboratory-reared on Aphidius smithi, A. eadyi, and A. ervi. At 19°c adults lived for an average of 9.7 days; females produced 75 progeny, or 8.6 per day. The low fecundity relative to that of the host may be compensated for by greater life span at temperatures below 15°c. The threshold temperature for larval development was 7.8°c, 4.8°C higher than that of A. eadyi. However, at 25°c the time to adult emergence was similar for the primary parasite and hyperparasite. The Aphidius parasite is shown to be vulnerable to oviposition by Dendrocerus from the time of death of its aphid host to formation of the adult primary parasite. The seasonal pattern of hyperparasitisim was related to the abundance of mummies at a particular site. It is concluded from the average level of hyperparasitism (47%) that Dendrocerus species would be unlikely to affect overall population trends of A. eadyi. Where longer intervals between lucerne cuts favoured A. eadyi, hyperparasitism by Dendrocerus species also increased.